discrepancies in stress values of linear elastic axisymmetric model of a three-layered pavement

[ali-kho2]

Hello every one,
I have been performing a finite element analysis of load-deformation in a three-layered pavement system loaded by a uniform circular static loading in ABAQUS CAE. The nodal points are restrained both vertically and horizontally at the bottom layer; vertically at the radial direction and at the axis of symmetry, the nodal points are only free to vertical movement.
In the analysis of increasing the elastic modulus of the middle layer (base material) up to 2000 % in 4 increments, all the curves of vertical stress(S22), vertical strain (E22), horizontal stress (S11), horizontal strain (E11) converge to a turning point from where the trend of increase/decrease in respected(comparing each curve of the different elastic modulus) value is reversed. I don’t know how to interpret this behavior. I would appreciate any explanation.
Thanks in advance,

 

[FEA way]

Can you attach a picture of your model (with visible boundary condition symbols) or the files (cae/inp) ?

 

[ali-kho2]

Here are the model geometry and boundary conditions:
The Subgrade section partition was also assigned the material or section property of the subbase layer to simulate a three-layered system.

Thanks,

 

[FEA way]

Could you also show the deformed shape contour plot of the stress in the model ? It might be easier to interpret the results this way.

 

[ali-kho2]

Sure, thank you for your time.
here are the contours of vertical stress (S22), vertical strain (E22) horizontal stress (S11), and Horizontal Strain (E11).
thanks,